Coupling structures are commonly used for coupling a rotatable shaft to provide a driving arrangement with a driven structure. Internal combustion engines rely on coupling structures known as torsional vibration dampers to lessen the vibrations in rotatable shafts, such as the crankshaft, caused by intermittent applications of either power or load that are not smooth and continuous. Unless controlled, the vibrations may lead to shaft failure and may contribute to causing other parts of the engine or cooling system, particularly where resonance occurs, to fail. One familiar variety of conventional torsional vibration dampers include a metallic insert, a polymer hub surrounding the metallic insert, an inertia member radially outward of the polymer hub, and an annular elastomer layer disposed radially between the polymer hub and the inertia member.
Virtually all motor vehicles equipped with an internal combustion engine incorporates a serpentine drive belt system consisting of at least one endless drive belt and a series of pulleys. The pulleys derive power from the endless drive belt and operate to drive the vehicle accessory devices, such as the engine fan, power steering pump, air pumps, air conditioning unit, and the alternator. The endless drive belt that drives each of these pulleys is driven by a drive pulley connected to the crankshaft of the internal combustion engine. To reduce the transfer of vibrations between the crankshaft and the serpentine drive belt system, the drive pulley may comprise a torsional vibration damper that functions to reduces the amplitude or magnitude of the angular vibrations delivered by the crankshaft to the belt.
Conventional torsional vibration dampers are susceptible to irreversible structural damage when a gear puller is used to remove the torsional vibrational damper from the rotatable shaft to service the internal combustion engine or for use on a different engine. In use, the gear puller grasps the torsional vibration damper and applies a lateral force sufficient to disengage or pull it from the rotatable shaft. Due to the resistance provided by the press fit that captures the torsional vibration damper to the rotatable shaft, the lateral force that must be applied by the gear puller during removal is significant. The lateral force needed to remove the torsional vibration damper increases if the metallic hub is frozen to the rotatable shaft by corrosion, deformation, or the like. The large applied lateral forces may irreversibly damage the torsional vibration damper.
One observed failure mode is catastrophic mechanical damage to areas of polymer material contacted by the arms of the gear puller. Such mechanical damage can permanently unbalance the torsional vibration damper and thereby degrade its performance. In another common failure mode, the lateral force applied by the gear puller causes the metallic insert to separate from the polymer hub, such that the metallic insert remains attached to the rotatable shaft. In this instance, the torsional vibration damper is irreparably damaged.
There is a need, therefore, for a coupling structure capable of being removed from a rotatable shaft in an undamaged condition.